Police have made serious errors getting search warrants for suspected sex offenders, leading to the targeting of innocent people and children being wrongly separated from their parents, an official report has revealed.

The errors – highlighted by the interception of communications commissioner, Sir Stanley Burnton, in his annual report to the prime minister – had “appalling” consequences and related to some of the most intrusive powers the state can use against its citizens.

In one example, two children were separated from their parents for a weekend while the parents were questioned as suspects in a child sexual exploitation case. It later emerged that police had raided the wrong address due to an error on the documentation and the parents were innocent.

Digital devices belonging to innocent people were also forensically examined by police, Burnton said.

The errors identified were mainly because details were wrongly entered into software that helps police work out the location where a specific IP (internet protocol) address has been used.

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But IP addresses are routinely reassigned by internet providers. Burnton warned investigators not to rely on them when trying to work out who is hiding behind the anonymity of the internet to commit crimes.

He wrote: “These [errors] are far more common than is acceptable, especially in cases relating to child sex exploitation. The impact on some victims of these errors has been appalling.”

Burnton said there were 29 serious errors by those entitled to use intrusive powers – not just police – making up 0.004% of the total number of applications.

“The impact of these errors has, in some cases, been enormous. People have been arrested for crimes relating to child sexual exploitation. Their children have been taken into care, and they have had to tell their employers.”

Innocent people were treated as suspects and detained or had their homes and devices searched on seven occasions.

In other cases, two innocent people were arrested and interviewed under caution by officers investigating child sexual exploitation due to similar IP address errors.

An investigation into a paedophile ring saw the wrong person detained and interviewed after communications data was wrongly interpreted.

In one murder investigation, officers obtained a telephone number, but recorded it incorrectly in a database and contacted the wrong person.